[Fix] Don't write conv state from the fused KDA verify kernel (#39219)

Co-authored-by: mmangkad <mohammad.angkad@radixark.ai>

test/registered/kernels/test_fused_kda_conv_recurrent_verify.py

@@ -166,12 +166,12 @@ def _compare_case(case, num_warps):
 
     idx_vals = inp["idx_vals"]
     valid_rows = [i for i, slot in enumerate(idx_vals) if slot >= 0]
-    touched_slots = [slot for slot in idx_vals if slot >= 0]
 
     o_ref_v = o_ref.reshape(B, T, HV, V)[valid_rows]
     o_fus_v = o_fus.reshape(B, T, HV, V)[valid_rows]
     assert torch.equal(o_ref_v, o_fus_v)
-    assert torch.equal(conv_ref[touched_slots], conv_fus[touched_slots])
+    # conv_state is read-only in verify; the commit scatter advances it.
+    assert torch.equal(inp["conv_pool"], conv_fus)
     assert torch.equal(win_ref[valid_rows], win_fus[valid_rows])
     torch.testing.assert_close(
         ic_ref[valid_rows], ic_fus[valid_rows], atol=4e-3, rtol=0
@@ -183,5 +183,27 @@ def test_matches_unfused_reference(case):
     _compare_case(case, num_warps=4)
 
 
+def test_output_does_not_depend_on_cta_scheduling():
+    """The verify output must not change with how the CTAs happen to be
+    scheduled. H=1 with HV=16 shares one Q/K history across 16 V tiles."""
+    if torch.cuda.get_device_capability()[0] < 9:
+        pytest.skip("green contexts need SM90 or newer")
+    from flashinfer.green_ctx import split_device_green_ctx_by_sm_count
+
+    case = (1, 6, 1, 16, 128, 128, 4, False, None, False, 1)
+    B, T, H, HV, K, V, W, has_bias, lower_bound, neg_slot, seed = case
+    inp = _make_inputs(B, T, H, HV, K, V, W, has_bias, neg_slot, seed)
+    full = _run_fused(inp, B, T, H, HV, K, V, lower_bound, num_warps=4)[0]
+
+    streams, _ = split_device_green_ctx_by_sm_count(torch.device("cuda:0"), [8])
+    # The green stream is non-blocking, so it must be told to wait for the
+    # inputs produced above; synchronize() afterwards only waits on the consumer.
+    streams[0].wait_stream(torch.cuda.current_stream())
+    with torch.cuda.stream(streams[0]):
+        squeezed = _run_fused(inp, B, T, H, HV, K, V, lower_bound, num_warps=4)[0]
+    streams[0].synchronize()
+    assert torch.equal(full, squeezed)
+
+
 if __name__ == "__main__":
     sys.exit(pytest.main([__file__]))